Isometrus wayanadensis, Sulakhe & Deshpande & Gowande & Dandekar & Ketkar, 2022

Sulakhe, Shauri, Deshpande, Shubhankar, Gowande, Gaurang, Dandekar, Nikhil & Ketkar, Makarand, 2022, Arboreal gems: resurrection of Isometrus sankeriensis Tikader & Bastawade, 1983 and descriptions of two new species of Isometrus Ehrenberg, 1828 (Scorpiones: Buthidae) from the Western Ghats, India, European Journal of Taxonomy 811 (1), pp. 1-50 : 29-33

Isometrus wayanadensis sp. nov.

urn:lsid:zoobank.org:act:2FC053B2-9202-4A22-8149-CBBE556C27AF

Figs 13–17 , 18C , 19C, F , 21D , 23C , 25C ; Table 3

Diagnosis (♂ ♀)

Total length 41.29–50.99 mm. Base colouration yellowish-brown and variegated with black-brown stripes and spots. Basal segments of chelicerae dorsally yellowish with blackish reticulation. Pectinal tooth number 15–18 in both sexes. Median supra-ocular region smooth. Median ocelli anteriorly situated in ratio of 1: 2. Tergites I–VI sparsely and coarsely granular, with median carina stronger on posterior region. Isometrus wayanadensis sp. nov. differs from all other Indian species of Isometrus based on the following set of morphological characters:

1. Surface of carapace coarsely and densely granular ( Figs 14C , 18C ) as opposed to: coarsely and sparsely granular with some areas without granules in I. sankeriensis and I. thurstoni ; finely and densely granular in I. amboli ; granular throughout with mixed granules, more densely granular in inter-ocular area and median posterior ocular area in I. kovariki ; and granular throughout but obsolete in I. maculatus .

2. Chela length to width ratio in males 5.0–5.3 as opposed to 6.1–6.5 in I. tamhini , 5.7–5.8 in I. sankeriensis and 10.6 in I. nakshatra sp. nov.; in females 4.7–5.0 as opposed to 5.2–5.9 in I. tamhini , 5.7 in I. amboli , and 6.1–6.2 in I. nakshatra sp. nov. ( Tables 1–3 ).

3. Lateral patches on mesosomal tergites V and VI with fine granulation along margins ( Fig. 21C ) as opposed to coarse granulation along margins in I. tamhini .

4. Metasomal length to carapace length ratio in males 6.8–7.2 as opposed to 8.8–9.1 in I. tamhini , 5.9–6.1 in I. sankeriensis , 5.3–5.8 in I. nakshatra sp. nov., 7.6–8.2 in I. thurstoni and 9.6 in I. maculatus ( Tables 1–3 ).

5. Lateral supramedian and ventral lateral carinae on metasomal segments II–IV moderately granular ( Fig. 23C ) as opposed to strongly granular in I. tamhini and I. sankeriensis .

6. Telson length to width ratio in males 3.9–4.2 as opposed to 4.6–4.8 in I. tamhini and 4.3 in I. sankeriensis ( Tables 1–3 ).

7. Ventral median carina of telson vesicle moderately granular ( Fig. 19F ) as opposed to weakly granular in I. sankeriensis , I. thurstoni , I. kovariki and I. nakshatra sp. nov., and strongly granular in I. tamhini .

8. Spiniform granules of promedian carina of pedipalp patella strongly developed as opposed to moderately developed in I. tamhini , I. amboli , I. sankeriensis and I. kovariki , and weakly developed in I. nakshatra sp. nov. ( Figs 24–25 ).

Etymology

The species epithet indicates the type locality of the new species, Wayanad National Park, in Kerala, India.

Material examined

Holotype INDIA • ♂, adult; Kerala State, Wayanad District, Kidanganad ; 11.70° N, 76.30° E; 929 m a.s.l.; 26 Dec. 2019; Shauri Sulakhe and Aditya Grover leg.; BNHS SC 190 .

Paratypes INDIA • 1♂, adult; same locality as for holotype; 1 Nov. 2020; Makarand Ketkar, Shubhankar Deshpande, Shauri Sulakhe and Swayam Thakkar leg.; INHER 279 • 3 ♀♀, adults; same locality as for holotype; 1 Nov. 2020; Makarand Ketkar, Shubhankar Deshpande, Shauri Sulakhe and Swayam Thakkar leg.; INHER 278 , INHER 280 , INHER 281 • 2 ♀♀, adults; same collection data as for preceding; BNHS SC 191 , BNHS SC 192 • 1 ♂, adult; Karnataka State, Kodagu District , K.S. Colony ; 11.96° N, 76.05° E; 866 m a.s.l.; 1 Nov. 2020; Makarand Ketkar, Shubhankar Deshpande, Shauri Sulakhe and Swayam Thakkar leg.; BNHS SC 193 .

Description (holotype, ♂, measurements in Table 3 )

COLOURATION ( Fig. 13A–B ). Body and appendages yellowish and variegated with blackish brown stripes and spots; metasomal segment V dark brownish to blackish, darker on posterior portion; pedipalp fingers dark brownish. Ventral portion uniformly yellow and sternite VII with a few dark spots. Basal segments of chelicerae dorsally yellowish, with blackish reticulation ending anteriorly in a blackish transverse patch. Fingers of chelicerae dark brown with tip of fingers black. Telson reddish brown.

CARAPACE ( Figs 14C , 18C ). Surface coarsely and densely granular. Without carinae. Median supraocular area almost smooth on middle and posterior portion, distinctly granular on anterior portion. Inter-ocular area with coarse granules. Pair of median ocelli situated anteriorly, with median ocelli to anterior margin/median ocelli to posterior margin ratio of 1: 2. Antero-lateral ocular tubercle granular, with type 5 lateral ocelli. Three pairs of large major ocelli and two small minor ocelli situated behind major ocelli. Longitudinal furrow moderately deep all along. Anterior margins smooth. Lateral margins weakly crenulated below lateral ocelli. Posterior margin almost entirely smooth.

CHELICERAE ( Fig. 13D ). Characteristic of Buthidae . Basal segments and movable fingers with short, firm setae on basal and ventral surfaces.

PEDIPALP ( Figs 15 , 25C ). Femur with five carinae (prodorsal, retrodorsal, promedian, retromedian and proventral). All carinae crenulated. Intercarinal surfaces weakly granular except ventral surface smooth with a few fine granules on proximal portion. Patella with seven distinct carinae (dorsomedian, prodorsal, retrodorsal, retromedian, retroventral, promedian and proventral). Dorsal intercarinal surface weakly granular and ventral intercarinal surface smooth. Chela acarinate. Fixed fingers almost smooth. Movable and fixed fingers with six rows of prolateral and retrolateral denticles in pairs and single additional row of retrolateral denticles on proximal portion. Trichobothrial pattern typical for genus (chela dorsal 12, chela ventral 2, patella dorsal 6, patella retrolateral 7, femur dorsal 7 and femur prolateral 4).

LEGS ( Figs 13A–B , 14A–B ). Femur and patellae carinated. All carinae granular. Tibiae 3 and 4 without tibial spurs. All legs with a pair of pedal spurs. Tarsomere covered with long delicate setae arranged in parallel rows on ventral side. Tarsomere I (basitarsus) with tuft of short, stout blackish setae on ventral side. Tarsomere II (telotarsus) compressed laterally and ventrally with paired row of short, pointed, anteriorly directed, closely placed setae.

GENITAL OPERCULUM ( Fig. 13C ). Wider than long, elliptical, separated, with a pair of short male genital papillae.

PECTINES ( Fig. 13C ). Basal piece rectangular, deeply notched on anterior median margin. Posterior margin of basal piece curved. Marginal lamella of 3/3 digits and median lamella of 6/7 digits, outer margin armed with a row of stout, short red setae and a few setae on surface. Fulcra 15/15, roughly triangular, each armed with a few short red setae, placed in between adjacent pectinal teeth. Teeth 16/16, strong and stout.

MESOSOMA ( Figs 13A–B , 14A–B , 21C ). Tergites I–VI sparsely and coarsely granular, with median carina more strongly developed on posterior side. Posterior and lateral margins granular. Lateral patches on mesosomal tergites V and VI with fine granulation along posterior margins. Tergite VII granular, narrowed posteriorly, with two pairs of lateral granular carinae. Broad median carina present, more strongly developed on anterior portion. Sternites III–VI almost entirely smooth, with a pair of spiracles. Sternite VII smooth on posterior margin, finely crenulated to serrated on lateral margins; two pairs of granular carinae with median carina present on posterior portion and lateral carina present along entrire length.

METASOMA ( Figs 13A–B , 14A–B , 23C ). All segments longer than wide. Segment I with five pairs of granular carinae (dorsal lateral, lateral supramedian, lateral inframedian, ventral lateral and ventral submedian). Intercarinal surfaces almost smooth. Segments II–IV with four pairs of carinae (dorsal lateral, lateral supramedian, ventral lateral and ventral submedian). Dorso-lateral and ventro-lateral carinae moderately granular. Lateral carina present on segment I only. Lateral supramedian and dorsal lateral carinae posteriorly ending in pointed, sub-triangular tubercles, more pointed on segments II and III. Intercarinal surfaces more granular on ventral portion. Segment V with five carinae (lateral supramedian pair, ventral lateral pair and single ventral median). Intercarinal surfaces finely granular. Anal rim almost smooth.

TELSON ( Fig. 19C, F ). With elongated vesicle, smooth on dorsal surface. Ventral median carina moderately granular on distal portion, ending in triangular, subaculear, pointed nodule, armed with two pairs of minute denticles on inner margin. Ventral portion with two weak carinae. Lateral and ventral intercarinal surfaces weakly granular on distal portion only. Aculeus moderately elongated and sharp.

Distribution, habitat and ecology ( Figs 17 , 26 )

Isometrus wayanadensis sp. nov. is known from the type locality, Kidanganad, Wayanad District, Kerala State, India, and one more locality, K.S. Colony, Kodagu District, Karnataka State, India, which is ca 60 km from the type locality. The new species is found under tree bark on tall trees in the moist deciduous and evergreen forest of Wayanad National Park (NP). A dense population of the new species was observed in the forest along the roads near the type locality. Wayanad NP is contiguous with Nagarhole NP, Bramhagiri Wildlife Sanctuary, and Bandipura NP and Tiger Reserve (TR) in Karnataka, and with Mudumalai NP and TR in Tamil Nadu, where the new species may occur in these protected areas; however, this needs to be confirmed with more sampling. The ecology of the new species is congruent with bark scorpions.

Figures

Fig. 13. Isometrus wayanadensis sp. nov., holotype, adult ♂ (BNHS SC 190). A. Dorsal view. B. Ventral view. C. Sternopectinal area. D. Chelicera, dorsal view.

Fig. 14. Isometrus wayanadensis sp. nov., holotype, adult ♂ (BNHS SC 190). A. Dorsal view, UV light. B. Ventral view, UV light. C. Carapace, white light.

Fig. 15. Isometrus wayanadensis sp. nov., holotype, adult ♂ (BNHS SC 190). A–B. Pedipalp chela. A. Dorsal view. B. Ventral view. C–D. Patella. C. Dorsal view. D. External view. E–F. Femur. E. Dorsal view. F. Internal view. Trichobothrial pattern indicated by yellow dots.

Fig. 16. Isometrus wayanadensis sp. nov., paratype, adult ♀ (BNHS SC 191). A. Dorsal view. B. Ventral view. C. Carapace, dorsal view. D. Sternopectinal area. E. Telson, lateral view.

Fig. 17. Type locality of Isometrus wayanadensis sp. nov. Views of tall evergreen forest along road at the type locality.

Fig. 18. Carapace under UV light. A. Isometrus sankeriensis Tikader & Bastawade, 1983, neotype, adult ♂ (BNHS SC 194). B. I. nakshatra sp. nov., holotype, adult ♂ (BNHS SC 195). C. I. wayanadensis sp. nov., holotype, adult ♂ (BNHS SC 190).

Fig. 19. A–C. Telson in lateral view. D–F. Telson in ventral view. A, D. Isometrus sankeriensis Tikader & Bastawade, 1983, neotype, adult ♂ (BNHS SC 194). B, E. I. nakshatra sp. nov., holotype, adult ♂ (BNHS SC 195). C, F. I. wayanadensis sp. nov., holotype, adult ♂ (BNHS SC 190).

Fig. 21. Mesosomal tergites V and VI in dorsal view under UV light. A. Isometrus sankeriensis Tikader & Bastawade, 1983, neotype, adult ♂ (BNHS SC 194). B. I. nakshatra sp. nov., holotype, adult ♂ (BNHS SC 195). C. I. wayanadensis sp. nov., holotype, adult ♂ (BNHS SC 190).

Fig. 23. Metasoma in lateral view under UV light. A. Isometrus sankeriensis Tikader & Bastawade, 1983, neotype, adult ♂ (BNHS SC 194). B. I. nakshatra sp. nov., holotype, adult ♂ (BNHS SC 195). C. I. wayanadensis sp. nov., holotype, adult ♂ (BNHS SC 190).

Fig. 25. Comparison of left pedipalps. A. Isometrus sankeriensis Tikader & Bastawade, 1983, neotype, adult ♂ (BNHS SC 194). B. I. nakshatra sp. nov., holotype, adult ♂ (BNHS SC 195). C. I. wayanadensis sp. nov., holotype, adult ♂ (BNHS SC 190).

Fig. 24. Comparison of left pedipalps. A. Isometrus thurstoni Pocock, 1983, topotype, adult ♂ (INHER 139). B. I. tamhini Sulakhe et al., 2020, holotype, adult ♂ (BNHS SC 155). C. I. amboli Sulakhe et al., 2020, holotype, adult ♂ (BNHS SC 157). D. I. kovariki Sulakhe et al., 2020, holotype, adult ♂ (BNHS SC 161).

Fig. 26. Distribution of Indian species of Isometrus Ehrenberg, 1828 with elevation data. Stars represent type localities and circles represent additional sampled localities.